Robotic automated welding of cylindrical parts has become increasingly common. Current methods of welding the cylindrical parts rely on coordinated motion between a welding robot and a positioner robot configured to position and rotate the cylindrical part. Due to inconsistencies in a geometry of the cylindrical part or a misalignment during the mounting of the cylindrical part to the positioner robot, it is common for a welding operation performed on the cylindrical part to be tracked in a manner wherein offsets to be applied to the path of the welding operation to compensate for the variations in the part geometry. These offsets often require relatively small movements of the welding robot, often leading to an instance of welding robot draft in each of a travel direction and a lateral direction of the welding operation.
One method of tracking the weld joint position may include a stationary tracking process. One problem present in traditional stationary tracking processes is that in the absence of coordinated motion the stationary tracking process cannot provide a relative motion speed between the tracking device and the object being tracked. In the case of the welding of a cylindrical part rotated about its rotational axis, a move time of the welding robot and a rotational speed of the positioner robot must each be specified prior to the welding operation to achieve a desired relative travel speed for the welding operation. This requirement adds difficulty and time to the setup of the welding process. Additionally, each time a new cylindrical part having a different geometry is mounted to the positioner robot the robot move time and the rotational speed of the positioner robot must be recalculated once again.
To solve this problem a method of coordinated stationary tracking may be employed. One known method includes positioning the welding torch of the welding robot at a specified position relative to the cylindrical part from which the tracking is to occur. During the initial pass of the welding robot the cylindrical part is tracked and the determined offsets to be applied to the welding robot are stored to memory relative to the base of the welding robot. However, this process results in a situation where each subsequent welding pass will have to start and stop at the same position relative to the base of the welding robot because the offsets are stored relative to the base of the welding robot. This problem severely limits the use of this method of stationary tracking when multiple welding passes are required and especially when at least some of the additional passes are staggered relative to each other.
It would therefore be desirable to provide a method of stationary coordinated tracking that allows for the offsets to be applied during the welding operation to be determined relative to the geometry of the cylindrical part to be welded and not relative to a base of the welding robot.